Particle classifier



Dec. 28, 1965 U. N. BHRANY PARTICLE CLASS IFIER Filed Aug. 50. 1961 INVENTOR. UPENDRA N. BHRA N) MXQW United States Patent 3,225,927 PARTICLE CLASSIFIER Upendra N. Bhrany, Wilkinsburg Borough, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Filed Aug. 30, 1961, Ser. No. 134,924 2 Claims. (Cl. 209-479) rates a sample of particulate material into a plurality of size fractions.

A further object is to provide a classifier of the foregoing type which overcomes difficulties commonly encountered in a screening operation, namely that screen openings become plugged with near-size and odd-shaped particles.

A more specific object is to provide a classifier which includes a stepped tray and a vibrator for vibrating the tray at varying amplitudes along its length, whereby particles fed to the tray accumulate at different locations thereon depending on their size.

In accomplishing these and other objects of the invention. I have provided improved details of structure, a preferred form of which is shown in the accompanying drawing, in which:

The single figure is a longitudinal vertical sectional View of a classifier constructed in accordance with my invention.

My classifier comprises essentially a vibrator 10 and a stepped tray 12 mounted on the vibrator. The vibrator per se is of conventional construction and includes a stationary base 13, a sloping end plate 14 fixed to the rear of the base, an electromagnetic mechanism 15 fixed to the back face of plate 14, and a reciprocable shelf 16 operated by the electromagnetic mechanism. The front portion of base 13 carries a bracket 17 to which are fixed a pair of upstanding leaf springs 18. A metal strip 19 of inverted L-shape is fixed at one end to the top of the leaf springs and at the other end to the top of shelf 16. This strip has slots 20, through which bolts 21 extend to attach the strip to the shelf, whereby the strip can be adjusted with respect to the shelf to vary the tension in the leaf springs. As known in the art, the electromagnet is operated through an adjustable controller (not shown) which rapidly and repeatedly energizes and deenergizes the electromagnet. As the electro-magnet is energized, it pushes shelf 16 and strip 19 rearwardly (toward the left as viewed in the drawing) and upwardly with a sharp motion. As the electromagnet is de-energized, springs 18 return the shelf and strip to their original positions, but the motion is less sharp than the first motion. The frequency and relative speed of these motions can be varied by adjusting the spring tension and the power input to the electromagnet. Vibrators of this construction and controllers therefor are available commercially from the Syntron Company, Homer City, Pa. and are described in more detail in their printed publication entitled Syntron Vibratory Material Handling Equipment, Catalogue 598.

In accordance with my invention, tray 12 is removably mounted on the front portion of strip 19 and it slopes downwardly toward the front of the classifier (toward the right as viewed in the drawing). The upper face of strip 19 carries front and back pivot ears 22 and 23, and the underface of the tray front and back pivot ears 24 and 25. The front pivot ears 22 and 24 are directly pivoted together, while the back pivot ears 23 and 25 are connected through a slotted link 26. These parts normally are rigidly bolted together, but I can adjust the slope of the tray on loosening the bolts. The upper face of the tray carries a plurality of steps formed of treads 27 and risers 28. I can obtain a further adjustment by changing to trays proportioned differently. In operating my classiiier, there are six independent control variables, as folows:

(a) power supply (b) slope of the tray (c) angle between riser and tread (d) height of riser (e) width of tread (f) numbber of steps As already pointed out, I adjust (a) by varying the spring tension and power input; I adjust (b) by varying the position of pivot ear 25 with respect to link 26; and I adjust (c), (d), (e) and (f) by using differently proportioned trays.

In operation, I feed a sample of particulate material to the tread 27 of the top step, and start the vibrator. Larger particles tend to move along each tread toward the next step to a greater extent than smaller particles. The extent of movement of the tray decreases from the back (left) toward the front (right), since springs 18 act somewhat as a fulcrum for the tray, Thus the decreased motion enables the different steps to effect separations at different sizes, and I am able to obtain a Whole series of size fractions on different steps.

As an example to demonstrate how my classifier operates, I set up my classifier with a tray 12 of twelve steps having its underface at an angle of 37 with the horizontal and the steps sloping downwardly toward the front at an angle of 9 with the horizontal. I operated vibrator 10 at an intensity of vibration 60 percent of allowable, and I fed a gram sample of particulate material to the top step. A screen analysis of the sample showed the following size distribution:

TABLE I Analysis of feed Size: Percent by wt. +20 0.77 20+50 74.17 -50+100 13.02 100+200 6.80 200+270 2.17 270+325 1.32 325 1.75

After five minutes on my classifier, the sample was separated into four size fractions. A screen analysis of the fractions showed the following size distribution in each:

TABLE II Analysis of fractions Had I desired a different size split, I could have changed any one of the variables hereinbefore tested or any combination of these variables.

From the foregoing description it is seen my invention affords a classifier of simple construction for separating a sample of particulate material into a plurality of size fractions. The classifier avoids the usual difficulties encountered in screening a sample.

While I have shown and described only a single embodiment of my invention, it is apparent that modifications may arise. Therefore, I do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.

I claim:

1. A classifier for separating particulate material into size fractions comprising a vibrator and a tray, said vibrator having a base, an electromagnetic mechanism supported on the back portion of said base, a movable shelf operatively connected to said electromagnetic means, an upstanding leaf spring carried by the front portion of said base, and a strip fixed at its ends to said shelf and said leaf spring, said tray being supported on the front portion of said strip and sloping toward the front and having a plurality of treads and risers forming steps along its upper face, said vibrator vibrating said shelf, strip and 20 tray as said electromagnetic means is energized and deenergized to throw larger particles of a sample down the steps to the exclusion of smaller particles, said spring acting as a fulcrum to move the back portion of the tray through greater distances than the front portion.

2. A classifier for separating particulate material into size fractions comprising a support, a tray having front and back portions, spring means attached to said support and to the front portion of said tray and fulcruming said tray, a vibrator on said support, and means operatively connecting said vibrator with the back portion of said tray, said tray sloping downwardly from its back portion toward its front portion and having treads and risers forming a series of steps along its upper face, whereby said tray moves sharply in one direction with the back portion moving through a greater distance than the front portion, said spring means returning said tray in the other direction with a less sharp movement, thus throwing larger particles of the material down the steps to the exclusion of smaller particles.

References Cited by the Examiner UNITED STATES PATENTS 1,482,607 2/1924 Gow 209471 XR 1,988,720 1/1935 Coyle 209-504 XR 2,312,665 3/1943 Moore 209-481 XR FOREIGN PATENTS 63,234 5/ 1949 Netherlands.

HARRY B. THORNTON, Primary Examiner.

Examiners. 

1. A CLASSIFIER FOR SEPARATING PARTICULATE MATERIAL INTO SIZE FRACTIONS COMPRISING A VIBRATOR AND A TRAY, SAID VIBRATOR HAVING A BASE, AN ELECTROMAGNETIC MECHANISM SUPPORTED ON THE BACK PORTION OF SAID BASE, A MOVABLE SHELF OPERATIVELY CONNECTED TO SAID ELECTROMAGNETIC MEANS, AN UPSATNDING LEAF SPRING CARRIED BY THE FRONT PORTION OF SAID BASE, AND A STRIP FIXED AT ITS ENDS TO SAID SHELF AND SAID LEAF SPRING, SAID TRAY BEING SUPPORTED ON THE FRONT PORTION OF SAID STRIP AND SLOPING TOWARD THE FORNT AND HAVING A PLURALITY OF TREADS AND RISERS FORMING STEPS ALONG ITS UPPER FACE, SAID VIBRATOR VIBRATING SAID SHELF, STRIP AND TRAY AS SAID ELECTROMAGNETIC MEANS IS ENERGIZED AND DEENERGIZED TO THROW LARGER PARTICLES OF A SAMPLE DOWN THE STEPS TO THE EXCLUSION OF SMALLER PARTICLES, SAID SPRING ACTING AS A FULCRUM TO MOVE THE BACK PORTION OF THE TRAY THROUGH GREATER DISTANCES THAN THE FRONT PORTION. 